//根据圆的半径
var p = Math.PI;
var n = prompt("请输入圆的半径");
n = Number(n);
//圆的周长
var c = 2*p*n;
//圆的面积
var d = p*n*n;

console.log(n);
console.log(c);
console.log(d);

document.querySelector("#a").value = n;
document.querySelector("#b").value = c;
document.querySelector("#c").value = d;

